(584c) Vortical Interactions in Nature

From swimming to aerial flights, organismal vortical interactions are ubiquitous in nature. In this work, we explore how organisms from jellyfish to fruit flies exploit vortical interactions to enhance their propulsion efficiency and minimize their cost of transport. While prior studies focused on organisms interacting with vortices in bulk fluids, we examine the organismal vortical interactions at air-water interface using water walking Microvelia as a case study. These insects use an alternating tripod gait, where their hind tarsi interact with the vortices shed from their middle legs, where they exhibit wake capture phenomenon where the prior vortices are re-energized enhancing their thrust on water. We evaluate the role of the spatiotemporal orientation of hind legs in vortical interactions of Microvelia. Using dimensionless analysis, we compare vortical interactions across organisms of varying size and shape, locomoting in air, water and in between. This comparative approach offers a universal framework for understanding the role of vortical interactions in nature.